The present invention relates to a screening method for a multi-layered ceramic capacitor for guaranteeing the insulation resistance characteristic of the multi-layered ceramic capacitor.
Conventional screening methods for a multi-layered ceramic capacitor for guaranteeing the insulation resistance characteristic of the multi-layered ceramic capacitor include:
a withstand voltage testing method of applying a direct-current voltage exceeding a rated voltage several times repeatedly between external electrodes of the multi-layered ceramic capacitor, electrically breaking down defective parts of the dielectric ceramic layer, and removing the portions lowered in an insulation resistance;
an insulation resistance measurement testing method of measuring an insulation resistance after a specific time has passed from applying a direct-current voltage, and removing the portions not returning to the criteria value; and
a leak current measurement testing method of measuring the leak current after a specific time has passed from applying a direct-current voltage, and removing the portions exceeding the criteria value,
and by these methods, defective parts have been sorted out.
A higher insulation resistance characteristic is required for multi-layered ceramic capacitors. When evaluated by an acceleration test of applying a voltage exceeding the rated voltage in a high temperature and high humidity environment, a multi-layered ceramic capacitor being lowered in the insulation resistance value may however be determined out of ones approved by the conventional screening methods.
The present invention solves the problem of the prior art, and it is hence an object thereof to present a multi-layered ceramic capacitor capable of guaranteeing a high reliability without causing a deterioration of an insulation resistance characteristic even by an acceleration reliability test.
To solve the problem, the present invention is designed to superpose a direct-current constant current between external electrodes of a multi-layered ceramic capacitor, raise the voltage between the external electrodes, feed the direct-current constant current for a specific time after the voltage curve comes to show a flat characteristic, and sort and remove as a defective one if the voltage between the external electrodes drops suddenly during the feeding time.
According to this method, it is free from a deterioration of an insulation resistance characteristic even in the acceleration reliability test.